Bicycles are a popular and efficient form of transportation that allow riders to travel over long distances with relative ease. Bicycles are also environmentally friendly and allow riders to exercise while they travel. As bicycle designs have progressed, numerous improvements have been implemented to enhance various aspects of bicycle performance.
Some modifications, like multi-gear drive systems, make bicycles easier to operate over hills and during periods of heavy wind. Additionally, new seat designs have made bicycles more comfortable, increasing the distance they may be ridden. Some bicycles, like recumbents, even allow riders to assume a reclined orientation during travel. Other bicycles include provisions to accommodate more than one rider simultaneously. Still other bicycles, like those of U.S. Pat. No. 4,400,003 and U.S. Pat. No. 5,052,706 have components that are selectively collapsible to promote easy storage and safe shipping.
In addition to providing a practical means of transportation and a convenient source of exercise, bicycles are often used as a source of entertainment. For example, many riders explore rocky terrain on so-called "mountain bikes." This type of bicycle typically includes a shock absorbing suspension system that improves control over uneven surfaces. Suspension systems reduce rider fatigue by absorbing impacts that would otherwise be transmitted directly to the rider. An example of a suspension-including bicycle is disclosed in U.S. Pat. No. 5,658,001.
Mountainous terrain is not the only location traversed by thrill-seeking bicycle riders, however. Many riders choose the bicycle as a means of simulating temporary flight. Typically, this flight experience involves riding a bicycle at high speed up, onto, and over an inclined ramp. The bicycle's momentum carries the bicycle and rider through the air.
Ramp jumping, although thrilling, can be very dangerous; a wide variety of variables affect the outcome of a given jump. For example, approach speed, ramp angle, and even tire pressure must all be within given acceptable ranges for a jump to be successful. Misjudgment, lack of concentration, or poorly maintained equipment may all lead to a failed jump, resulting in possible injury or even death. As a result, ramp jumping is not an activity that is safe for all riders.
Regardless of the dangers involved, many bicycle riders attempt ramp jumping as a pastime. In addition, television promotes such events making it alluring to even the most unsophisticated riders. Unfortunately, few riders have the requisite knowledge and skill to jump ramps successfully. Many riders are injured because they perform jumps without understanding the dynamics involved. To make matters worse, most bicycle modifications do not make ramp jumping safer.
U.S. Pat. No. 5,301,969 is one known disclosure that provides a dual frame bicycle for purposes of jump simulation. The bicycle converts rotational energy from the bicycle back wheel into translational energy used to make the bicycle leap. The '969 device is formed from two frames and employs a hooked pole that selectively engages a pin affixed to the bicycle rear wheel. The two bicycle frames are spaced apart by elastic members, and using the hooked pole to engage the rear wheel pin draws the two frames together, storing potential energy in the elastic members. The pole remains hooked to the wheel pin while until the wheel has rotated a predetermined distance, at which point the hook is released. When the hook is released, the energy stored in the elastic members is released, forcing the bicycle frames apart and causing the bicycle to jump.
The '969 requires a two-frame construction that is cost prohibitive and, once the bicycle begins to store energy, a jump is unavoidable. Even if it were possible to wrench the hook free from the wheel pin before the wheel had rotated through the hook-releasing distance, the already-stored energy would still be released. As a result, a rider attempting to abort a jump will still be lifted before coming to rest. This design also makes it difficult for a rider to increase or decrease the amount of lift, as needed. The '969 produces consistent amounts of lift which may not be appropriate for all situations during a given bicycle ride.
What is lacking in the prior art is a single frame bicycle that allows a rider to experience the thrill of jumping, without requiring the rider to undergo the equipment preparation and skill set development associated with jumping over a ramp. The bicycle should provide a rider-controlled positioning means for raising the rider from a standard position to an elevated position and then safely returning him to the standard position. The bicycle should be able to elevate the rider without requiring that the bicycle become airborne. The bicycle should be customizable to provide varying degrees of lift to suit riders of different stature. The bicycle should also be customizable to provide different lifting characteristics, including varied lift rates and lift heights.